Excitation and decay of Isoscalar Giant Dipole Resonance

Excitation and decay of Isoscalar Giant Dipole Resonance • • Introduction on Giant Resonance A schematic model of GR Excitation of ISGDR in 58 Ni (a, a`) reaction Experimental details Data Analysis Results and discussions Summary and conclusions

Giant Resonance: Coherent vibration in a nucleus. of nucleons A Schematic Model of GR: The H 0 to denote the Hamiltonian operator of a nucleon in the central potential of the single particle shell model. In the transition of the particle from a full shell to the one above , we must also take the particle-hole interaction into account ; the Hamiltonian operator then be written as The collective excitations appear just because of the mixing generated by this particle-hole interactions V.

Nucleus Many body system with a finite size Vibration Multi-pole expansion with r, Ylm, t, s DS=0, DT=0 DS=0, DT=1 DS=1, DT=1 L=0: Monopole ISGMR r 2 Y 0 L=1: Dipole L=2: Quadrupole ISGDR t Y 0 IVGDR r 3 Y 1 tr. Y 1 ISGQR IVGQR r 2 Y 2 L=3: Octupole IAS LEOR, HEOR r. Y 3, r 3 Y 3 t r 2 Y 2 IVGMR t r 2 Y 0 t r 3 Y 1 GTR t s Y 0 SDR ts r. Y 1 ts r 2 Y 2 IVSMGR t s r 2 Y 0 ts r 3 t. Y 1

Isoscalar Excitation Modes of Nuclear Resonance Giant Resonance: Coherent vibration of nucleons in a nucleous. Resonances due to imcompressibility : ISGMR, ISGDR Nuclear matter

ISGMR, ISGDR KVI (1977) TAMU(2000) Large instrumental background! 励起の弱いISGDRを議論する には不十分。

D. H. Youngblood et al. , RIKEN Rev. 23, 159(1999) Y. -W. Lui et al. , PRC 61, 067307 (2001)

Measurement Details • 386 Me. V a @RCNP 58 Ni, 90 Zr, 116 Sn, Sm, 208 Pb • 0 -13 deg (Angular range) • Elastic scattering : 3. 5 -25 deg range. Nucleus Angles (degree) Excitation energy(Me. V) 58 Ni 0 -13 10 -35 -52 90 Zr 0 -13 10 -35 116 Sn 0 -13 10 -35 Sm 0 -13 10 -35 208 Pb 0 -13 10 -35

RCNP Ea=386 Me. V DEa = 250 ke. V@FWHM Halo free beam ~10 counts/ 1 n. A @ empty target, 0 degs.

. • RCNP facility K=400 Me. V ring cyclotron Grand Raiden spectrometer • Beam： – 4 He++, 386 Me. V • Target: 58 Ni foil 5. 8 mg/cm 2

GRAND RAIDEN SPECTROMETER

Instrumental Background VDC Y-position

Typical Spectra Excitation Energy Spectra at 0 o Angular Distribution

Excitation Energy Spectrum

Multipole decomposition analysis (MDA) • • DWBA 計算 ・・・ Ptolemy Folding Model

DWBA Formalism: Transition Potential:

Transition density • ISGMR G. R. Satchler, Nucl, Phys, A 472 (1987) 215 • ISGDR M. N. Harakeh, Phys. Rev. C 23 (1981) 2329 • Other modes Bohr-Mottelson(BM) model

58 Ni

Transverse flow SN 1987 A

CONCLUSIONS q. A two component ISGDR strength distribution has been obtained for the first time in 58 Ni q. ISGDR strength distribution is in excellent agreement with recent QRPA predictions. q The value of incompressibility of infinite nuclear matter( Knm ) is 217 Me. V as obtained from global systematic of present study.